Retroreflective materials are commonly employed for safety and decorative purposes. One type of retroreflective material is formed of molded members having very small prisms or cube corner formations. See, for example, U.S. Pat. No. 3,810,804.
It is often desirable to apply these materials to pre-existing structures; in which case, the retroreflective material may not be compatible with the material of the pre-existing structure or the method of application may be destructive of the retroreflective properties.
A need exists, therefore, for a retroreflective system and process in which the retroreflective material may be fabricated to facilitate permanent transfer to existing structures of different material without damaging the retroreflective material.
A method and apparatus for forming retroreflective material on a substrate are described in which a release coating is formed on a base material and an array of solid light transparent prisms are formed on the coating by casting the prism array in a plastic oligomer which is adhered to the coating.
The prisms are then made reflective by forming a metal layer on the prisms.
In one embodiment, an adhesive is then applied to the reflective metal layer. A substrate is then applied to the adhesive and the base material is removed at the release coating, leaving an exposed array of free-standing retroreflective prisms, that is prisms with a reflective metal backing affixed to the substrate. In an alternate embodiment, before the adhesive is applied, the prism array may be stripped from the base material at the release coating, thereby freeing the individual prisms in the array. The freed prisms may then be dispersed in a paint or a transparent binder for example, for the purpose of printing retroreflective images on fabrics or painting various substrates.
The substrate is preferably formed of the same material as the structure upon which the retroreflective material is to be secured or is compatible with such structure. For example, the substrate may comprise a sheet of synthetic resin, such as polyvinyl chloride (PVC), polyamide, polypropylene, polycarbonate, or fabrics such as polyester, nylon, or the like, coated with a suitable resin.
Preferably, the substrate with the exposed prism layer may then be covered with a transparent protective layer on the exposed side and the substrate may then be bonded by various well-known techniques to a pre-existing structure of the same or similar material as the substrate.
Alternatively, the adhesive may be a heat activated adhesive applied to the array before metallization. Strips spaced across the length of the array sheeting may then be laminated to a substrate leaving an air space between the array and substrate backing to provide a low cost retroreflective sheet on a suitable substrate fabric.